The former Red Devils centre-back joined the club the season before the Portuguese and played alongside him as he attempted to establish himself in the Premier League.

The young Ronaldo always showed he had the potential to become the best player in the world, but Ferdinand, speaking in the brilliant Four Four Two documentary 'Relentless' above, remembers a time when he had yet to fulfil his own prophecy.

Rio Ferdinand reveals the moment Cristiano Ronaldo became a "game-changer" for Man United (Image: Getty Images)

In the clip, the now 38-year-old ex-defender recalls the early days in the future Real Madrid star's career, and pinpoints the very moment he transformed from a good player to a "game-changer".

He begins by reminiscing on what Ronaldo was like in training, and explained how other players at the club, including Gary Neville, introduced him to English football.

"He liked taking liberties when he first came, taking people on, making people look silly and doing skills before coming back to beat them again," says Ferdinand.

Rio admits Ronaldo was shown some "tough love" when he first signed for the Red Devils

The former centre-back reveals how both Neville brothers would at times be the "butt of his joke" but that they would respond with some "tough love" to help with his development.

Ferdinand adds: "His whole thing when he first signed was about showmanship, he'd listen to the fans when he'd do that bit of skill, when he'd do that step-over.

Ferdinand explains that once the "penny dropped" Ronaldo became one of the world's best players (Image: John Peters)

"Whereas then there was that turning point around that time when it was about goals, assists. Then he became the game-changer, rather than the showman."